Add deprecation notices for <% %>.

  * The approach is to compile <% %> into a method call that checks whether
    the value returned from a block is a String. If it is, it concats to the buffer and
    prints a deprecation warning.
  * <%= %> uses exactly the same logic to compile the template, which first checks
    to see whether it's compiling a block.
  * This should have no impact on other uses of block in templates. For instance, in
    <% [1,2,3].each do |i| %><%= i %><% end %>, the call to each returns an Array,
    not a String, so the result is not concatenated
  * In two cases (#capture and #cache), a String can be returned that should *never*
    be concatenated. We have temporarily created a String subclass called NonConcattingString
    which behaves (and is serialized) identically to String, but is not concatenated
    by the code that handles deprecated <% %> block helpers. Once we remove support
    for <% %> block helpers, we can remove NonConcattingString.

1 files changed, 2 insertions, 2 deletions

diff --git a/actionpack/test/fixtures/layouts/block_with_layout.erb b/actionpack/test/fixtures/layouts/block_with_layout.erb
index f25b41271d..73ac833e52 100644
--- a/actionpack/test/fixtures/layouts/block_with_layout.erb
+++ b/actionpack/test/fixtures/layouts/block_with_layout.erb
@@ -1,3 +1,3 @@
-<% render(:layout => "layout_for_partial", :locals => { :name => "Anthony" }) do %>Inside from first block in layout<% "Return value should be discarded" %><% end %>
+<%= render(:layout => "layout_for_partial", :locals => { :name => "Anthony" }) do %>Inside from first block in layout<% "Return value should be discarded" %><% end %>
 <%= yield %>
-<% render(:layout => "layout_for_partial", :locals => { :name => "Ramm" }) do %>Inside from second block in layout<% end %>
+<%= render(:layout => "layout_for_partial", :locals => { :name => "Ramm" }) do %>Inside from second block in layout<% end %>